Process for treating cellulosic material



Patented Mar. 6,- i928.

UNITED STATES PATENT er/Pica;

FREDERICK CARL NIEDERHAUSER AND HAYDEN BENJAMIN KLINE, F CLEVELAND, I vOHIO, ASSIGNOBS TO THE INDUSTRIAL RAYON CORPORATION, OF CLEVELAND,

OHIO.

Noni-swing.

depth or shade of color by the use of dyestuffs and coloring matters normally employed for this purpose.v We are familiar with the use of such salts asthe compounds of iron, chromium, etc. in the dyeing of cellulllosic materials, but they form no claim in this invention. Copper-saltsv have found to be unsuitable in our hands for this purpose v on account of producing streaks in bleaching,

causing uneven dyeing and for other reasons, so Metals, which like lead form highl illilsoh e ave uble sulfates are inapplicable. found the best results obtained in our process'for increasing. the evenness of dyeing of viscose rayon and viscose products by the use of a water-soluble zinc salt, or a zinc salt,

compound or derivative which may be transformed into a water-solublestate, and of the zinc salts, their value for this pur in general is'in proportion to their rea y-solubility in water or in the solutions or mixtures constituting the various setting baths us] ally employed in viscose filament manufacture. The use of zinc carbonate is not advised, due to the evolutionoflcarbondioxide u from the inor anic acid normally present in the precipitating bath.

It is not material as to the comp ingredients or their proportion present inQth e setting bath for ,the viscose, the addition 40 thereto of relatively small amounts of zinc,

zinc compounds or derivatives, we have obtained excellent results in' evenness of dyeing when but 0.02% of zinc in solution was present in the precipitatlng or setting bath in II which the viscose was coagulated. However,

' general P f employ larger amounts referably up to about, 0.9% of elemental zinc by weight to 100 arta by ose conversant with the of viscose viscose rayon or product "within "dyes and developed .colors.

ifilht of the spin bath. As is we known PROCESS FOR TREATING CELLULOSIC MATERIAL. I

Application filed September 20, 1927. Serial No. 220,834.

manufacture, there is wide variation in physical properties of various batches or runs of viscose at the point where it is coagulated or precipitated, depending upon the degree and length of time-of ripening or maturing of the alkali-cellulose and afterwards of the xanthated cellulose, so that a fixed optimum amount of zinc in solution cannot be stated by us at the present moment to obtain the maximum ofevennessand exhaustion from bath in the subsequent dyeing of the viscose which has been precipitated inthe presence of the relatively minuteamount of zinc in solution. I

The method of introduction of the zinc salt into the setting bathis relatively unimpoi-taut, either. a solid salt introduced directly; Where the solubility, like zinc sulfate, is high, or, the salt may be dissolved separately and added to the viscose setting bath in amounts desired to obtain the dyeing results required,

The percentage of zinc found in the finished viscose rayon when treated by our process varies with the efliciency of the subsequent washing steps and the type of finish- 1ng process used; The percentage of zinc and coloring matters. That is, the amount .remainingin the washed and bleached mof zinc retained in theviscose filament or I fiber may be nearly indistinguishable analytically, and still the peculiar and advantageous effect in respect to dyeing remains. 'It would appear that the minute amounts of zinc, acting catalytically, or otherwise, may

change the constitution of the regenerated cellulose suflicient to. exhibit the enhanced; reactivityto coloring matters, and especially affinity for a large range of dyestuifs. Of the dyestuffs especially applicable to our process are the 'Indanthrene?-oup, i

has been noticed that upon introduction into the setsmall "amounts specified, the"o"subsequent ting bath of zinc in solutionin the relatively bleaching process f' invariably produces a.:

whiter cellulosic material The bleaching and desulfurizing in the process of produc' viscose rayon, are not materially modified y the introduction of the zinc in solution in the amounts found especially useful by us.

In connection with the manufacture of viscose filaments which are afterwards to be dyed, there is distinct economies effected in the amount of dyestuff required to produce a given depth of shade, because when zinc is used in the step of the process indicated and in substantially within the limits stated, viscose yarn or film will dye to a deeper shade with the same amount of dyestufi', on account of more nearly complete exhaustion of the dyebath, where the viscose has been coagulated in a normal setting bath/to which has been added small amounts of zinc in solution.

It should be emphasized that treatment of viscose by our process as herein stated does not result in an inferior product after bleaching, nor is there observable a marked decrease in the tenacity and other desirable characteristics of the finished filament, fiber or film.

a The remarkable dyeing properties exhibited are far out of proportionto the amount of zinc which is retained in the finished .product, we having demonstrated that zinc introduced into the finished fiber in the manner herein described, when as little as 10 to 20 parts per million of zinc is found in the ash, such yarn "will dye many shades darker than will yarn spun in the same manner' from a portion of ripened viscose which has been precipitated in a bath not containing zinc, but otherwise of identical composi- .tion. i

statement in our experience, holds true for as high concentrations as equivalent to 0.7% elemental zinc in the finished fiber.

It would appear that the presence of zinc in the amounts advocated herein, in the bath used for precipitation of the ripened viscose exerts a specific efiect resulting in a variation in the character, agglomeration or configuration of the micells or cellulose structural entities. This variation in intrinsic composition is not alone manifested in the specific character of the cellulosic material towards dyestuffs, but is further exemplified in the p ysical characteristics of, the yarn. For instance, the extensibility of viscose rayon is constantly increased by the presence of small amounts of zinc in the spinning solution,

and it has been pointed out in many instances in the literature, that increased dye absorptiveupowers are usually accompanied by high cell osic extensibility.

We are aware of the United States Patent 1,045,731 granted to Sidney S. Napper for a process which results in superior products and in economy of working by the use of a coagulating bath containing zinc sulfate and glucose; and we are aware of the British Patent 216,125 granted to L A/Bergen for the-use of magnesium sulfate in combination with a zinc salt. We make no claim to or for the above.

Having now described our invention and in what manner the same may be performed, what we claim and desire to secure by Letters Patent is:

- 1. A process for increasing the levelness and evenness in dyeing of cellulosic material obtained by the precipitation of viscose in an aqueous bath consisting of an inorganic polybasic acid, an alkali metal salt of the same, and containing zinc dissolved therein, the amount of said zinc not exceedin 0.9% of the weight of the precipitating bat said viscose after preci itationbein trea in a known manner 0 washing, esulfurizing, bleaching and dyeing, as set forth herein.

2. A process for increasing the dye absorptive capacity of cellulosic material obtained by the precipitation of viscose in an aqueous bath, consisting in precipitating the viscose in an aqueous bath consisting of a dibasic inorganic acid, an alkali metal salt of the same, and of relatively small amounts of zinc in the dissolved state, then treatin said viscose in a known manner, substantia ly as described herein.

3. A method for effecting economy in the dyeing of that form of cellulosic material obtained from the precipitation of solutions containing viscose, comprising introducing the viscose solution into a precipitating bath consisting of sulfuric acid of strength desired, an alkali metal salt of the same, and zinc in solution in amount not exceeding ninetenths of one percent of zinc based on the weight of the precipitating solution, afterwards treating the precipitated viscose by ways now known, as set forth herein.

4. A process for the introduction into cellulosic material such as hydrated cellulose obtained from the coagulation and other treatment of viscose in solution, of small amounts 'of zinc, comprising precipitating said viscose solution in an aqueous bath consisting of a polybasic inorganic acid, combinations of the same with an alkali metal, and a soluble form of a zinc salt not exceeding 0.9% of zinc based upon the weight of the coagulating bath, afterwards washing, desulfurizmg, bleaching, and d eing the cellulosic material obtained from t e precipitation of the viscose, by ways now known as set forth herein.

5. A process for increasing evenness, levelness, amount of cellulosic material dg'ed per unit weight of. coloring material an desir- III washing desulfurizing bleaching and dyeing the product obtained, by ways now 10 5 known as set forth herein.

In testimony whereof we have signed our names to this specification.

FREDERICK CARI. NIEDERIIAUSER. HAYDEN IENJAIIN KLINE, 

